1. Technical Field
The present invention relates to a liquid jet head which jets liquid droplets onto a recording medium to perform recoding and a liquid jet apparatus.
2. Related Art
Recently, there has been used a liquid jet head of an ink jet system that ejects ink droplets onto a recording paper or the like to record characters or figures thereon, or ejects a liquid material onto the surface of an element substrate to form a functional thin film thereon. In the ink jet system, liquid such as ink and or a liquid material is guided from a liquid tank into a channel through a supply tube, and pressure is applied to the liquid filled in the channel to thereby eject the liquid as liquid droplets from a nozzle that communicates with the channel. When ejecting liquid droplets, characters or figures are recorded, or a functional thin film having a predetermined shape is formed by moving the liquid jet head or a recording medium.
In JP 7-178903 A, there is described an edge shoot liquid jet head 100 which has a plurality of grooves formed on a piezoelectric body substrate as channels for ejecting liquid and ejects liquid droplets from ends of the grooves. FIG. 8A is a schematic cross-sectional view of the liquid jet head 100 in a direction perpendicular to the grooves as channels. FIG. 83 is a schematic cross-sectional view of an ink chamber 103 in the groove direction. The liquid jet head 100 is provided with a piezoelectric ceramic plate 102, a cover plate 110 which is bonded to an upper surface of the piezoelectric ceramic plate 102, and a nozzle plate 114 which is bonded to a side surface of the piezoelectric ceramic plate 102. In the piezoelectric ceramic plate 102, grooves 119 which constitute the ink chambers 103 and grooves 104 in which liquid is not filled are alternately arranged with partition walls 106 interposed therebetween. The cover plate 110 is adhered to the upper surface of the piezoelectric ceramic plate 102 through an epoxy resin 120. A manifold 121 is formed on the cover plate 110. The manifold 121 communicates with the ends of the grooves 119 so that ink can be supplied. A PZT ceramic plate is used as the piezoelectric ceramic plate 102. The piezoelectric ceramic plate 102 is polarized in a polarization direction 105.
The grooves 104 are formed by performing cutting so as to penetrate the cover plate 110 up to the piezoelectric ceramic plate 102. In each of the partition walls 106 which partition the grooves 119 and the grooves 104, a metal electrode 108 is formed on one side surface facing an ink chamber 103, and an electrode 117 is formed on the other side surface facing a groove 104. The metal electrodes 108 are formed above the center in the depth direction of the grooves 119, and extracted as metal electrodes 109 to shallow grooves 107 on the side of an end surface 115 of the piezoelectric ceramic plate 102, the end surface 115 being located opposite to the nozzle plate 114. The electrode 117 is formed on inner side surfaces and a bottom surface of each of the grooves 104 and a flat portion 116 of the cover plate 110. The electrodes 117 is set to a common potential, and a drive signal is applied to the metal electrodes 109 to cause pressure waves in liquid filled in the ink chambers 103, thereby ejecting liquid droplets from nozzles 112.
In the liquid jet head 100 described in JP 7-178903 A, it is necessary to allow a large number of metal electrodes 109 to be exposed on an upper surface of the piezoelectric ceramic plate 102 at the side of the end surface 115 located opposite to the nozzle plate 114. Therefore, the length in the groove direction of the piezoelectric ceramic plate 102 is required to be longer than the width of the cover plate 110. Further, the grooves 104 are formed by performing cutting from the cover plate 110 using a diamond blade. When forming the grooves 104, it is necessary to prevent the diamond blade from reaching the manifold 121, and therefore form the grooves 104 so as to be separated from the manifold 121. Therefore, the length in the groove direction of the piezoelectric ceramic plate 102 is made longer.
Further, the electrode 117 formed on the grooves 104 is formed across an adhesive layer which is formed of the epoxy resin 120 between the piezoelectric ceramic plate 102 and the cover plate 110. When the material of the piezoelectric ceramic plate 102 and the material of the cover plate 110 are different from each other, distortion is likely to occur on the boundary due to a thermal expansion difference. Further, since the partition walls 106 are movable walls, a mechanical stress always acts. Therefore, the electrode 117 passing across the epoxy resin 120 may be broken, and it is difficult to configure the liquid jet head 100 with high reliability.